Various gypsum products, including wall panels, ceiling panels and tiles, are commonly used in the construction industry. Many of these gypsum products are made by preparing an aqueous gypsum slurry with calcined gypsum (calcium sulfate alpha hem ihydrate, calcium sulfate beta hemihydrate and/or calcium sulfate anhydrate), shaping the slurry and then allowing the slurry to harden by rehydrating calcined gypsum into gypsum (calcium sulfate dihydrate).
Gypsum panels can be manufactured by sandwiching a gypsum slurry between two cover sheets known as facers. In some applications, a facer is a paper sheet. Such wallboards in which a gypsum slurry is sandwiched between two sheets of paper find many different applications in building construction. However, wallboards may be sensitive to moisture and at least in some applications, other facer materials such as fibrous mats can be used as described for example in U.S. Pat. No. 8,329,308 and US Patent Publication 2010/0143682, both to the United States Gypsum Company, and the teachings of which are incorporated herein by reference. Suitable fibrous mats further include those disclosed in U.S. Pat. No. 5,772,846 and which are made with glass fibers and polyester fibers bound together.
While gypsum panels made with glass fiber mats have many advantages, the main disadvantage comes from the glass fiber mat structure in which there are voids between glass fibers, as shown in a micrograph of FIG. 1, which may affect consistency and compressive strength of a resulting gypsum panel. Further, glass fibers are brittle and this may negatively affect certain properties of a resulting gypsum panel, such as nail-pull strength which translates into a suboptimal ability for the panel to hold a nail.
US Patent Publication 2011/0086214 laminates one of the glass mat surfaces with a stiffening layer before the mat can be used in making a gypsum product. US Patent Publication 2002/0187296 discloses an assembly line on which a glass fiber mat is vibrated so that voids in the mat are more evenly filled with a gypsum slurry. However, while these methods fill out glass fiber mat voids, they do not address various issues such as suboptimal nail-pull strength because of brittle glass fibers.